In some medical applications, it may be necessary to dynamically track targets that move with time. For example, in radiation treatment it may be desirable to dynamically track tumors and/or lesions in the human body that move with respiration and/or heartbeat. In radiation treatment, accurate trajectories of the radiation beams through the patient anatomy to the lesion or tumor being treated can be critical, in order to achieve the radiation dose distribution that was computed during treatment planning time. For regions of the human anatomy that move, for example due to breathing or heartbeat, it is important to take such motions into consideration during treatment planning. Dynamic tracking may also be useful in applications other than radiation treatment in which parts of the anatomy move, due to breathing, heartbeat, or any other type of motion.
There are multiple different techniques that can be used to track a pathological anatomy (e.g., tumor or lesion) during treatment. Some tracking techniques have a high chance of success (e.g., a low chance that the anatomy's location will be reported incorrectly or that it's position will be undeterminable using the tracking technique), but a low accuracy, thereby requiring treatment of an increased amount of healthy tissue to ensure treatment of the full pathological anatomy. Other tracking techniques have lower chances of success, but a high accuracy. Therefore, when the tracking successfully works, less healthy tissue is treated.
One challenge in image guided treatment, such as radiation treatment, is determining which tracking technique to use for a patient. In conventional radiation treatment systems, a physician determines a tracking method to use for a patient based primarily on that physician's personal knowledge and expertise. Conventional treatment planning systems and treatment delivery systems do not include tools for performing simulation, testing potential tracking methods during the simulation, or analyzing simulation results to identify optimal tracking methods for tracking a target in the patient. Accordingly, some users create a treatment plan under an assumption that a particular tracking method will work, and later discover at treatment time that he cannot treat the patient because the chosen tracking technique cannot successfully track the pathological anatomy. This necessitates the generation of an entire new treatment plan, which wastes a medical physician's time, and adds considerable cost to treatment of the patient. For other patients, users generate treatment plans based on less than optimal tracking methods, i.e., methods providing less conformality (the degree to which a radiation dose matches the shape and extent of the target) and/or accuracy than other or optimal tracking methods, because users have good certainty the tracking method will work. The resulting sub-optimal treatment plan results in delivery of unnecessary radiation to healthy tissue.